Kidney fibrosis is a common final pathway of chronic kidney disease (CKD) leading to end- stage renal failure (ESRD) and specific anti-fibrosis therapy is lacking. Therefore, there is an urgent need to develop effective anti-fibrosis therapy t prevent the progression of CKD. It is known that the kidney fibrosis process is regulated by a complex cell signaling network. The drugs targeting these signaling pathways are of great interest. However, only a few drugs are in early phase of clinical trials. From the systems point of view, kidney fibrosis has a complex pathogenesis and drugs targeting individual signaling pathways may not have sufficient anti-fibrosis effects to prevent the progression of CKD. Therefore, it is important to perform systems analysis of the signaling network. During the last funding period we developed a combined systems biology and experimental approach allowing us to deduce upstream signaling networks from genome-wide gene expression profiles. Using this approach, we identified HIPK2 as a key regulator of genes altered in the kidney of animal model with kidney fibrosis. Furthermore, we confirmed that HIPK2 expression is increased in kidney biopsies from patients with various kidney disease associated with kidney fibrosis. In vitro, we found that HIPK2 mediates injury and activation of pro-fibrosis markers in kidney cells. HIPK2 activates multiple pro-fibrosis and pro-inflammatory signaling pathways leading to kidney fibrosis and inflammation. The role of HIPK2 in kidney fibrosis was also confirmed in mice with HIPK2 deficiency. Our findings indicate that HIPK2 is a key protein kinase mediating kidney fibrosis and suggests that it may be a potential drug target for anti-fibrosis therapy. In this competitive renewal application, we propose to further validate HIPK2 as a drug target for anti-fibrosis therapy and develop specific inhibitors of HIPK2 as anti-fibrosis drugs. These questions will be addressed in the following three specific aims: Specific aim 1: We will determine whether conditional knockout of HIPK2 in kidney cells attenuates kidney fibrosis in the animal models of kidney fibrosis. We will also determine whether the induction of HIPK2 expression in kidney cells accelerates renal fibrosis in these animals. Specific aim 2: We will determine the cellular and molecular mechanisms by which HIPK2 causes kidney fibrosis. Specific aim 3: We will identify specific and potent HIPK2 inhibitors and validate the effects of these inhibitors in cultured kidney cells and animal models of kidney fibrosis.